Light for residential and industrial lighting is generally provided by incandescent or fluorescent lights. Such lights generally consume significant power, are inefficient, and can also produce undesired heat. One potential replacement for such lights may be the use of gallium nitride light emitting diodes (LEDs). Gallium nitride devices may be formed by growing a gallium nitride film on silicon, sapphire, spinel or silicon carbide. A p-type layer and a n-type layer are grown with appropriate doping, contacts are formed by known methods and light emission is obtained by application of a suitable voltage. The gallium nitride layer may be alloyed with aluminum or indium to adjust the output wavelength to be appropriate for the particular application. Light output is typically in the violet, ultraviolet, blue or green regions of the spectrum.
Typically the light output from a gallium nitride LED is monochromatic and is unsuitable for white lighting. To obtain a white light output, the LED is coated with a phosphor which absorbs the monochromatic LED output and converts the light to broadband white light. These devices are already appearing in the market, but with very low light outputs.
Another problem with gallium nitride based lamps today is that in order to operate at light levels which are useful for general lighting, much higher power outputs are required. At the same time, smaller lamp sizes are required to make the lamps affordable. These are presently opposite requirements.